devtrackers.gg
Power is one of the things that always catches me as there's no obvious visual indication when you're running on low power (as opposed to completely disconnected), you just kind of notice all your production lines aren't as backed up as they ought to be and then figure it out.
There is low power status in the gui (and tooltip) of every electric entity in 1.1 (which is still experimental), also there is tip&trick about that, so once 1.1 becomes stable it should happen less often.